The present invention relates to a camera equipped with a cam member which is interlocked with the movement of a lens barrel holding a zoom lens and changes the magnification of a zoom viewfinder, and to a molding die for a camera-use cam member.
A camera equipped with a photographic lens composed of a zoom lens has a zoom viewfinder to change magnification in association with zooming. That is, when a lens barrel holding the zoom lens is moved toward the optical axis direction by zooming, a cam plate having a cam surface is moved in association with the lens barrel. In the zoom viewfinder, a variable magnification lens to move in the optical axis direction is provided, and a cam pin is protruded from the variable magnification lens or a lens frame to hold the variable magnification lens, and engaged with the cam surface of the cam plate. Accordingly, by the movement of the cam plate, the variable magnification lens is moved in the optical axis direction, and the magnification of the zoom viewfinder is changed.
In FIG. 8, an example of the cam plate is shown in an enlarged sectional view. Two cam pins 51 and 52 are protruded from the variable magnification lens of the zoom viewfinder optical system, and it is assumed that a side wall of the cam pin 51 is in contact with a cam surface 53a of a cam plate 53, and a side wall of the cam pin 52 is in contact with a cam surface 53b of a cam plate 53. Generally, the cam plate 53 is resin molded, and because it is drawn from the molding die to the upper direction of the drawing, the drawing slope is necessary for the cam surfaces 53a and 53b, and the inclination surface is provided as shown in the drawing in the exaggeration. As a metallic die to mold such the cam plate 53, conventionally, a metallic die (as shown in FIGS. 9(a) and 9(b)) is well known. An upper surface metallic die 100 to mold the upper surface side of the cam plate 53 is moved upward, and a lower surface metallic die 200 to mold the lower surface side is moved downward. Herein, specifically, in the case where the cam plate 53 is molded circular arc-like, corresponding to the shape of the lens barrel, when the draft angle is not provided as the cam surfaces 53a and 53b, the drawing can not be conducted from the metallic die after the molding.
Herein, in practice, a fluctuation of the dimension of the variable magnification lens, a fluctuation of the assembling position of a frame holding the zoom viewfinder optical system, and a fluctuation of the assembling position of the cam plate 53, are generated. Therefore, as shown in FIG. 8, sometimes, the relative position of the cam plate 53 to the cam pins 51 and 52 fluctuates to the upper or lower direction from the position of the solid line to the position of the broken line. As the result, because the contact positions of the cam pins 51 and 52 with the cam surfaces 53a and 53b fluctuate in the left and right directions, the position of the variable magnification lens fluctuates in the left and right directions, that is, fluctuates in the optical axis direction of the zoom viewfinder optical system, resulting in that an accurate magnification change operation is not conducted.
In view of the foregoing problems, the present invention is attained, and the first object of the present invention is to propose a camera in which, even when the cam pin or cam plate is fluctuated upward or downward, the position of the variable magnification lens is not fluctuated in the optical axis direction.
Further, the second object of the present invention is to propose the molding die for the camera-use cam member by which such the cam plate is molded.
Further, in the case where the cam plate is held in the gap between the lens barrel holding the zoom lens and the case holding the zoom viewfinder optical system, when the cam plate is moved left and right, the pressing by the frame becomes insufficient and the cam plate is floated. Then, the cam surface is tilted from the reference position, and the accurate cam driving can not be conducted.
The third object of the present invention is to propose the camera in which such the floating of the cam plate is prevented by a simple structure.
The above object is attained by the following structure.
1. A camera having the following structure, which comprises: a lens barrel holding a zoom lens; a zoom viewfinder optical system having a variable magnification lens to be moved in the optical axis direction; a cam pin integrally provided with the variable magnification lens; and a cam member to move the variable magnification lens being interlocked with the movement of the lens barrel, wherein the cam member has the cam surface provided with a protruded portion which comes into contact with only a portion of a side wall of the cam pin.
2. A molding die for a camera-use cam member having the following structure, which comprises: a cam surface molding member including a cam surface molding surface to mold the cam surface, which comes into contact with the cam pin integrally provided with the variable magnification lens of the zoom viewfinder optical system, and moves the variable magnification lens in the optical axis direction, following the movement of the lens barrel to hold the zoom lens; and a movement mechanism to move the cam surface molding member so that the cam surface molding surface moves in the almost perpendicular direction to the cam surface, wherein the cam surface molding surface includes a protruded portion molding surface to mold the protruded portion, by which the cam surface is brought into contact with only a portion of the side wall of the cam pin.
Further, the first object mentioned above is solved by the following structure.
A camera which comprises: a lens barrel to hold a zoom lens; a zoom viewfinder optical system having a variable magnification lens to be moved in the optical axis direction; a cam pin protruded from the variable magnification lens or a lens frame to hold the variable magnification lens; and a cam member, having a cam surface which comes into contact with a side wall of the cam pin, and driving the cam pin being interlocked with the movement of the lens barrel, the camera is characterized in that the cam surface comes into contact with the side wall of the cam pin only at the end portion on the variable magnification lens side, and the cam surface except for the end portion is retreated from the side wall of the cam pin.
The second object is solved by the following structure.
A molding die for a camera-use cam member to mold the cam member, which has a cam surface to come into contact with a side wall of a cam pin protruded from a variable magnification lens which is moved in the optical axis direction and changes the magnification of a zoom viewfinder optical system, or from a lens frame to hold the variable magnification lens, and which drives the cam pin being interlocked with the movement of a lens barrel to hold a zoom lens, the molding die for a camera-use cam member is characterized in that: the cam surface comes into contact with the side wall of the cam pin only at the end portion on the variable magnification lens side, and the cam surface except for the end portion is retreated from the side wall of the cam pin, and the metallic die to mold the cam surface is moved in the direction almost perpendicular to the axial direction of the cam pin.
The third object is solved by the following structure.
A camera which comprises: a lens barrel to hold a zoom lens; a zoom viewfinder optical system having a variable magnification lens to be moved in the optical axis direction; a case to hold the zoom viewfinder optical system; a cam pin protruded from the variable magnification lens or a lens frame to hold the variable magnification lens; a cam member, having a cam surface which comes into contact with a side wall of the cam pin, and driving the cam pin being interlocked with the movement of the lens barrel, and arranged in the gap between the lens barrel and the case, the camera is characterized in that, irrespective of the movement position of the cam member, a floating prevention member integrally formed with the case is arranged above at least a portion of the cam member.